001/*
002 *  Licensed to the Apache Software Foundation (ASF) under one
003 *  or more contributor license agreements.  See the NOTICE file
004 *  distributed with this work for additional information
005 *  regarding copyright ownership.  The ASF licenses this file
006 *  to you under the Apache License, Version 2.0 (the
007 *  "License"); you may not use this file except in compliance
008 *  with the License.  You may obtain a copy of the License at
009 *  
010 *    http://www.apache.org/licenses/LICENSE-2.0
011 *  
012 *  Unless required by applicable law or agreed to in writing,
013 *  software distributed under the License is distributed on an
014 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 *  KIND, either express or implied.  See the License for the
016 *  specific language governing permissions and limitations
017 *  under the License. 
018 *  
019 */
020
021package org.apache.directory.server.dns.io.encoder;
022
023
024/**
025 * 3. The DNAME Resource Record
026 * 
027 *    The DNAME RR has mnemonic DNAME and type code 39 (decimal).
028 * 
029 *    DNAME has the following format:
030 * 
031 *       <owner> <ttl> <class> DNAME <target>
032 * 
033 *    The format is not class-sensitive.  All fields are required.  The
034 *    RDATA field <target> is a <domain-name> [DNSIS].
035 * 
036 *    The DNAME RR causes type NS additional section processing.
037 * 
038 *    The effect of the DNAME record is the substitution of the record's
039 *    <target> for its <owner> as a suffix of a domain name.  A "no-
040 *    descendants" limitation governs the use of DNAMEs in a zone file:
041 * 
042 *       If a DNAME RR is present at a node N, there may be other data at N
043 *       (except a CNAME or another DNAME), but there MUST be no data at
044 *       any descendant of N.  This restriction applies only to records of
045 *       the same class as the DNAME record.
046 * 
047 *    This rule assures predictable results when a DNAME record is cached
048 *    by a server which is not authoritative for the record's zone.  It
049 *    MUST be enforced when authoritative zone data is loaded.  Together
050 *    with the rules for DNS zone authority [DNSCLR] it implies that DNAME
051 *    and NS records can only coexist at the top of a zone which has only
052 *    one node.
053 * 
054 *    The compression scheme of [DNSIS] MUST NOT be applied to the RDATA
055 *    portion of a DNAME record unless the sending server has some way of
056 *    knowing that the receiver understands the DNAME record format.
057 *    Signalling such understanding is expected to be the subject of future
058 *    DNS Extensions.
059 * 
060 *    Naming loops can be created with DNAME records or a combination of
061 *    DNAME and CNAME records, just as they can with CNAME records alone.
062 *    Resolvers, including resolvers embedded in DNS servers, MUST limit
063 *    the resources they devote to any query.  Implementors should note,
064 *    however, that fairly lengthy chains of DNAME records may be valid.
065 * 
066 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
067 */
068public class DnameRecordEncoder
069{
070}